The present invention relates to a denture mold which is utilized in dental techniques for making teeth prostheses, as well as to a method of and an arrangement for manufacturing such denture molds.
Methods of manufacturing such denture molds are known in the art. In accordance with known methods, pins which are utilized for anchoring a positive copy of several teeth or teeth groups on a base, are arranged with the aid of different auxiliary devices so that they preferably point toward the center of the chewing face of the clinical tooth crowns in the impression. In accordance with the known method, the pins are inserted by their needle-shaped projections directly into the denture impression at the predetermined locations. In accordance with another known method, each pin is fixed on the denture impression with the aid of a holding element formed by a slightly flexible brass wire. Also magnetic holding elements for pins are known wherein the pins are fixed on a curved frame above the denture impression. Finally, it is known to provide an arresting plate which has openings through which holding bars extend, and to mount the pins by short pipe pieces on the holding bars. All the above-mentioned methods utilize auxiliary devices for exact fixing of the pins relative to the denture impression. This has the disadvantage in the fact that despite the provision of special holding elements, the exact arrangement of the pins is not guaranteed. The pins which are not exactly parallel make difficult the subsequent assembling and disassembling of the molds.
After fixing of the pins, the denture impression is filled with mold material, such as for example a special hardening gypsum. After hardening, the holding elements are removed from the pins. The pins are not anchored in the positive denture copy. After this, a gypsum base is formed on the mold face from which the pins extend. After the hardening of the gypsum base, its lower side is surface ground. After this, the individual teeth can be separated with the aid of a gypsum saw and later removed from the base for further working. This method is very difficult and time-consuming, inasmuch as it is necessary to wait for hardening of the gypsum base. Especially disadvantageous is the fact that, when the base is constituted of gypsum or other similar materials, volume variations because of hardening expansion take place and the mold does not exactly correspond to the original. The above-mentioned hardening expansion also causes expansion of the pin-receiving openings in the base, and exact location of the pins is no longer guaranteed. The exact location of the pins deteriorates during repeated disassembling of the mold, since during assembling the pin-receiving openings in the gypsum base are rubbed. As a result of these disadvantages, the teeth prostheses made with the aid of such molds must further be worked again with considerable time expenditures.
A further method of manufacturing a denture mold is disclosed in the German Offenlegungsschrift No. 2,455,144. In accordance with this method, first the denture model is manufactured, faced at its lower side, and then placed onto a flate plate. Then from the lower side a plurality of openings are produced in the plate and the pins are anchored in these openings. It is not disclosed how the pins are anchored in the teeth. During drilling of the openings in the plate, simultaneously openings in the teeth are drilled. This method has the disadvantage that during drilling in a gypsum mold, material particles can burst through and thereby an exact guidance of the pins in the denture mold is not guaranteed. Moreover, the facing of the hardened gypsum mold is difficult and time-consuming. Finally, still a further method of manufacturing denture molds is known in accordance with which the pins are anchored in the mold during hardening of the mold material. This method is disclosed in the German Offenlegungsschrift No. 2,653,743. However, in accordance with this method the plate serves only as an auxiliary tool for respective fixing the pins, and does not serve as a base for the final mold.